> I would however complain that the default terminal on macOS is really not very good and I always install iTerm2...
Apple’s terminal is one of the very few that passes the VT torture test and has support for double width and height attributes. Sadly, it doesn’t do overlines and doesn’t italicise my terminal font.
And it still cannot display powerline characters correctly.
I think it depends on a font supporting them correctly. I’m using a zsh prompt that uses them and it seems normal. Check https://github.com/rbanffy/3270font and let me know if it helps. I was thinking of adding the powerline symbols to the test renderings.